There is known a hypervisor that implements a virtual machine by controlling the physical resource of the physical machine. The hypervisor allocates part of the region of the physical memory, which is one of the physical resources, to a virtual machine when generating (starting up) the virtual machine, and releases the region of the physical memory allocated to the virtual machine when erasing (halting) the virtual machine. If the released region of the physical memory is allocated, without being cleared (initialized), to another virtual machine which is to be started up next, information relating to the virtual machine to which the part of the physical memory has been previously allocated may perhaps be stolen by the another virtual machine started up next. In contrast, when using a method of clearing all the part of the physical memory which is to be allocated to the virtual machine before generating the virtual machine, it takes more time for generating the virtual machine.
Patent Document 1 discloses a method in which the memory region of the storage device is not initialized at a timing when the memory region is allocated to the virtual machine, and when access from the virtual machine occurs, the accessed memory region is initialized as necessary. Non-patent Document 1 describes a method called dynamic memory. Further, Non-patent Document 2 describes that the method in Non-patent Document 1 does not work well in optimizing applications.